text: The invention relates to a device and a method for acquiring an absorption coefficient and a refractive index of a substance in a terahertz waveband. The device comprises a femtosecond laser, an optical splitter, a light delay unit, a THz emission source, a sample test device, a THz detector and a computer. The device and the method provided by the invention can utilize the same experiment test device to rapidly accurately measure and calculate the absorption coefficients and the refractive indexes of solid slices, solid powder and a liquid phase substance in a terahertz waveband.